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Abstract

The lizard species Salvator ‘Tupinambis’ merianae and Varanus ornatus evolved independently in South America and Africa but share similar ecology and feeding behaviour, despite having notable differences in their skull structure. Tupinambis has a compact, relatively short and wide snout, whereas that of Varanus is more slender and narrow. In addition, a postorbital bar (POB) is present in Tupinambis but absent in Varanus, and the former lacks the mid-frontal suture that is present in the latter. Here, we explore the biomechanical significance of these differences using 3D computer-based mechanical simulations based on micro-computed tomography, detailed muscle dissections, and in vivo data. First, we simulated muscle activity and joint-reaction forces during biting using Multibody Dynamics Analysis. Then, the forces calculated from these models were used as an input for Finite Element Analysis, to investigate and compare the strains of the skull in these two species. The effects of the presence/absence of structures, such as the POB, were investigated by constructing artificial models which geometry was altered. Our results indicate that strains in the skull bones are lower in Tupinambis than in Varanus, in particular at the back of the skull. The presence of a POB clearly reduces the strains in the bones during posterior biting in Tupinambis, but not in Varanus. Our results hence highlight how the morphological differences between these two taxa affect the mechanical behaviour of their respective skulls during feeding.

Author Comment

This is an abstract which has been accepted for the SVPCA/SPPC 2017 conference

Marc E H Jones conceived and designed the experiments, performed the experiments, analyzed the data, contributed reagents/materials/analysis tools, reviewed drafts of the paper.

Susan E Evans conceived and designed the experiments, performed the experiments, analyzed the data, contributed reagents/materials/analysis tools, reviewed drafts of the paper.

Micheal J Fagan conceived and designed the experiments, performed the experiments, analyzed the data, contributed reagents/materials/analysis tools, reviewed drafts of the paper.

Flora Gröning conceived and designed the experiments, performed the experiments, analyzed the data, contributed reagents/materials/analysis tools, reviewed drafts of the paper.

Animal Ethics

The following information was supplied relating to ethical approvals (i.e., approving body and any reference numbers):

Ethische commisie dierproeven, Universiteit Antwerpen, Faculteit FBD provided full approval for the research from which we obtained the dead specimens.

Data Deposition

The following information was supplied regarding data availability:

We present the first results of our study at the SVPCA conference. We are currently preparing an article based on these results and the raw data will be available online when it will be published.

Funding

This work was supported by the Biotechnology and Biological Sciences Research Council (BBSRC) (BB/H011668/1, BB/H011854/1, BB/M008525/1, BB/M010287/1, BB/M008061/1) who provided funding for this research and a Discovery Early Career Researcher Award DE130101567 (Australian Research Council) which currently supports MEHJ. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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